Radio shielding conduit connection



April 7, 1942. D. INGALLS RADIO SHIELDING CONDUIT CONNECTION Filed Aug.3, 1940 Arron/EY Patented Apr. 7, 1942 RADIO SHIELDING coNDUrrCONNECTION David Ingalls, Westfield, N. J., assignor to Titeiex MetalHose Co., a corporation of New Jersey Application August 3, 1940, SerialNo. 350,176

(Cl. 12B-169) 15 Claims.

The present invention relates to the provision of connections, havingthe desired characteristics, between shielding conduits for electricalconductors.

Although the invention may have other applications, it is especiallyadapted for the connection of ignition conductors for internalcombustion engines, and the conduits for such conductors, with thecasings and electrodes of spark plugs.

The invention is especially efficacious in connection with connectionsto spark plugs wherein the shielded conduit connected to the shieldingcasing of a spark plug is in the form of an elbow.

The main object of the invention is to provide a connection as referredto having a bushing whereby a solid and secure connection may be made,good electrical connection between the joined conduits may be secured.the joined conduits are sealed at their joint against ingress ofmoisture from the exterior and the shielding casing for the spark plugis sealed from the conduit connected thereto, while the ignitionconductor in one of the joined conduits, especially that of curved orelbow formation, is properly spaced, secured and insulated.

Other and ancillary objects of the invention will appear hereinafter.

In the accompanying drawing which illustrates the invention- Fig. 1 is avertical central section of a spark plug, radio shielding casingtherefor and radio shielding elbow connected to said casing, embodyingthe invention;

Fig. 2 is a section on the line 2--2 of Fig. 1;

Fig. 3 is a side view of the improved bushing employed in the assemblyof Fig. 1; and

Fig. 4 is a section on the line 4--4 of Fig. 3.

Referring to the drawing, the spark plug comprises a shell 2 which isadapted to be screwed into the engine block. Within the shell 2 isscrewed the nut or bushing 3 against the gasket or washer 4. A centralelectrode 5 is surrounded by rolled mica insulation 6 and has a head 1and an electrode 8 of conventional form. This central spindle orelectrode is gripped into the nut 3 so as to produce a gas-tight jointby forcing a compressible metal ring 9 forward in a tapered opening ofthe nut. Mica disk insulation I0 surrounding the central electrode andthe insulation 6 is confined between the ring 9 and the head 'I. A metalcylinder II extends upwardly from and is integral with the nut 3, itbeing understood, of course, that the shell 2 is also of metal.

This cylinder II has a lining I2 of rolled mica which is inserted fromthe upper end of the cylinder. The upper end of the insulating sleeve I2is bound by a metal ferrule I3 of U-section embracing the layers andpinched thereon. The casing comprising the cylinder II and lining I2 actas a radio shield for the spark plug.

The space in the lower part of the casing between the mica sleeves 6 andI2 is occupied by a stack I5 of mica washers bearing at its lower endupon the metal washer I6 resting upon the nut 3. The metal tubular elbowII of circular cross section is adapted at its outer end to be securedin any suitable'or well known manner to the shielding ignition conduitfor the cable I8, comprising the conductor I9 and the insulation 20carried thereby, extending toward the magneto or other source ofignition current, while the other end of the elbow I1 has a flange 2Iengaged by the nut 22 screw-threaded upon the metal cylinder II andadapted to draw the elbow and the cylinder toward each other. Theignition cable I8 extends through the elbow into the casing comprisingthe metal cylinder II and mica sleeve I2, the inner end 0f the conductorI9 passing through a hole in the center of a metal washer 23 which bearsagainst the end of the insulation 20. The end of the conductor I9 alsopasses through a peripherally grooved washer 24, the conductor I9 beingfanned out at its end and soldered so as to securely hold the washer 24against the washer 23 and the latter washer against the end of theinsulation 20.

Sprung into the groove of the washer 24 is the upper convolution of aspiral spring '25, the lower end of which bears upon a metal washer 26secured to the end of the central spark plug electrode 5 so thatconnection lis established from the ignition conductor I9 to the centralelectrode. The spring 25, however, is not secured to the washer 26 butmay be removed therefrom by un-screwing the nut 22 and drawing theignition cable upwardly when the spring 25 will be lifted oli" thewasher 26. Good contact of the metal spring 25 with the washer 26,however, is secured by the spring pressure of the spring 25 when theparts are in assembled condition.

The soft rubber bushing, the same being resilient, water-tight andflexible, as shown in Fig. 3 (before assembly in the spark plugconnection) is integrally formed and comprises the cylindrical portions2'I and 2'I on opposite sides of the laterally projecting ilange orenlarged portion 28 midway between its ends, this bushing having auniform bore 2S passing entirely through it. The dimensions of thecylinder may of course be made such as to cooperate with their relatedparts in the assembled structure. In the present instance, however, thecylinder 21' is of slightly smaller outside diameter than the cylinder21, to accommodate conditions within the spark plug casing. In theassembled structure, the bushing of Fig. 3 is telescoped over theignition cable I8, its inner end bearing against the washer 23 and, thebore 28 being slightly smaller than the cable I8, the bushing, byfreasonof its resiliency, tightly grips the cable. Ordinarily in assembling theparts, the rubber bushing of Fig. 3 is telescoped on the end of thecable 20, resiliently gripping the same and the washers 23 and 24 andthe spring 25 are assembled on the end of the cable as described. 'Ihecylindrical portion 21 is then inserted within the elbow I1 and also theenlarged portion 28 is partially inserted therein, the extent of itsentry therein being limited by the inwardly extending projections 38formed by punching the wall of the elbow I1 from the outside inwardly.This leaves a portion of the enlargement 28 extending beyond the end ofthe Ielbow and, the diameter of the iiange or enlargement being greaterthan the internal diameter of the elbow, the portion of the flangeentering the end of the elbow is compressed in a manner similar to thatof a cork forced within the I neck of a bottle whereby the flange 2B isresiliently pressed firmly and securely against the inner wall of theelbow I1 and forms a fluid-tight connection therewith.

The elbow, with its parts thus assembled, is then assembled with thespark plug casing comprising the metal cylinder II and its insulatinglining I2, by inserting the cylinder 21 into such casing, bringing theend of the elbow and the end of the casing into proper registry andscrewing the nut 22 upon the cylinder I I of the casing, The ends of theelbow and the casing will be drawn towards each other as the nut isscrewed up and such action will force the lower portion of the flange orenlarged portion 28 within the casingI the flange portion 28 beingcompressed tightly and resiliently against the circular wall of thecasing so as to form a fluid-tight joint similar to a cork placed in theneck of a bottle. The nut 23 is preferably screwed home so that themetal end of the elbow contacts the metal end of the casing therebyforming a good electrical connection between such radio shielding parts.If, however, the nut is not screwed entirely home, electrical connectionwill be made between the elbow and casing through the nut and the flange28 may be sufficiently entered within the spark plug casing to furnish auidtight joint even when the nut 23 is not screwed completely home.After assembly as described, the parts will be in the position as shownin the assembled view of Fig. 1. In such assembly the cylinder 21' isseparated from the lining I2 of the casing by a space 3l.

Above the flange 28 the cylindrical portion 21 of the soft rubberbushing extends into and its flexibility permits it to be curvedaccording to the curvature of the elbow. This portion 21 of the bushingtherefore properly spaces the ignition cable from the walls of the elbowat all points so that such cable cannot be misplaced so as to approachtoo closely or come in contact with the walls of the elbow whereby aflash-over might be caused, but the ignition cable is at all points heldat a maximum distance from the elbow walls, and the cable is securelyinsulated and guarded against flash-over in the elbow.

The ignition cable being resiliently gripped by the rubber bushing so asto form a water-tight connection and the flange or enlarged part 28forming fluid-tight connections at the end of the elbow and at the endof the spark plug casing, the Joint between the elbow and the casing issecurely sealed against the admission of moisture from the exterior andalso the spark plug casing is sealed oil from the elbow. Theconstruction thus fulfills a most desirable function, namely that theinterior of the cable conduit should not only be sealed againstadmission of moisture from the exterior, but the interior of the elbowand its connected shielded conduit should be shut oil from the sparkplug chamber s0 that no accumulation of moisture may be transmittedtherefrom to the spark plug.

The cylinder portion 21 of the bushing which extends below the washerportion 28 operates to hold the end of the ignition cable in properposition and stillen it as well as increases the diameter of theinsulation of the cable conductor so that flash-over from corona effector otherwise, is prevented.

I 'I'he bushing consisting of the cylinders 21 and 21 and the flange orenlargement 2B may be made of material having suitable characteristicsother than soft rubber, as for instance the synthetic rubber of which anexample is that known under the trade name of Neoprene With the partsassembled as described, the spring 25 will press upon the washer 26 andestablish good connection with the central electrode 5.

While theeinvention has been illustrated in what is considered its bestapplication it may have other embodiments without departing from itsspirit and is not therefore limited to the structure shown in thedrawing.

What I claim is:

1. The combination with a spark plug, of a radio shielding casingtherefor, a metal radio shielding conduit for a conductor cable to saidspark plug, a conductor cable extending through said conduit and intosaid casing, an integral, tubular, resilient, flexible,fluid-impervious, insulating bushing through which said cable passes,said bushing having an outwardly extending enlargement intermediate itsends and cylindrical portions of less diameter on each side of saidenlargement, said enlargement resiliently pressing against said casingand said conduit, one of said cylindrical portions of the said bushingextending into said conduit upon one side of said enlargement and theother of said cylindrical busliing portions extending into said casingupon the other side of said enlargement, means for securing said conduitand casing together with said bushing enlargement resiliently bearingupon said conduit and casing and means at the end oi said cable forconnecting it with an electrode of the spark plug.

2. The combination with a spark plug, of a radio shielding casingtherefor, a curved metal radio shielding conduit for a conductor cableto said spark plug, a conductor cable extending through said conduit andinto said casing, an integral, tubular, resilient, flexible,fluid-impervious, insulating bushing through which said cable passes,said bushing having an outwardly extending enlargement intermediate itsends and cylindrical portions of less diameter on each side of saidenlargement, said enlargement resiliently pressing against said casingand said conduit, one of said cylindrical portions of the said bushingextending into said conduit upon one side of said enlargement and theother of said cylindrical bushing portions extending into said casing',upon the other side of said enlargement, means for securing saidconduit and casing together with said bushing enlargement resilientlybearing upon said conduit and casing and means at the end of said cablefor connecting it with an electrode of the spark plug. .sg-

3. The combination with a spark plug, of a radio shielding casingtherefor, a metal radio shielding conduit for a conductor cable to saidspark plug, a conductor cable extending through said conduit and intosaid casing, an integral, tubular, resilient, exible, fluid-impervious,insulating bushing through which said cable passes, said bushing havingan outwardly extending enlargement intermediate its ends and cylindricalportions of less diameter on each side of said enlargement, saidenlargement resiliently pressing against said casing and said conduit,one of said cylindrical portions of the said bushing extending into saidconduit upon one side of said enlargement and the other of said cylinydrical bushing portions extending into said casing upon the other sideof said enlargement, means for securing said conduit and casing togetherwith said bushing enlargement resiliently bearing upon said conduit andcasing and means at the end of said cable for connecting it with anelectrode of the spark plug, the said bushing enlargement enteringpartially into said conduit and partially into said casing.

4. The combination with a spark plug, of a radio shielding casingtheretor, a metal radio shielding conduit for a conductor cable to saidspark plug, a conductor cable extending through said conduit and intosaid casing, an integral, tubular, resilient, flexible, Huid-impervious,insulating bushing through which said cable passes, said bushing havingan outwardly extending enlargement intermediate its ends and cylindricalportions of less diameter on each side of said enlargement, saidenlargement resiliently pressing against said casing and said conduit,one of said cylindrical portions of the said bushing extending into saidconduit upon one side of said enlargement and the other of saidcylindrical bushing portions extending into said casing upon the otherside of said enlargement, means-for securing said conduit and casingtogether with said bushing enlargement resiliently bearing upon saidconduit and casing and means at the end of said cable for connecting itwith an electrode of the spark plug, the said cylindrical bushingportion entering said casing being of smaller diameter than thecylindrical bushing portion extending into said conduit.

5. The combination with a spark plug, of a radio shielding casingtherefor, a metal radio shielding conduit for a conductor cable to saidspark plug, a conductor cable extending through said conduit and intosaid casing, an integral, tubularyresilient, flexible, huid-impervious,insulating bushing through which said cable passes, said bushing havingan outwardly extending enlargement intermediate its ends and cylindricalportions of less diameter on each side of said enlargement, saidenlargement resiliently pressing against said casing and said conduit,one of said cylindrical portions of the said bushing extending into saidconduit upon one side of said enlargement and the other of saidcylindrical bushing portions extending into said casing upon the otherside of said enlargement, means for securing said conduit and casingtogether with said bushing enlargement resiliently bearing upon saidconduit and casing and means at the end of said cable for connecting itwith an electrode of the spark plug, said tubular bushing resilientlypressing on said cable.

6. The combination with a spark plug, of a radio shielding casingtherefor, a metal radio shielding conduit for a conductor cable to saidspark plug, a conductor cable extending through said conduit and intosaid casing, an integral, tubular, resilient, flexible,fluid-impervious, insulating bushing through which said cable passes,said bushing having an outwardly extending enlargement intermediate itsends and cylindrical portions of less diameter on each side of saidenlargement, said enlargement resiliently pressing against said casingand said conduit, one of said cylindrical portions of the said bushingextending into said conduit upon one side of said enlargement and theother of said cylindrical bushing portions extending into said casingupon the other side of said enlargement, means for securing said conduitand casing together with said bushing enlargement resiliently bearingupon said conduit and casing and means at the end of said cable forconnecting it with an electrode of the spark plug, said bushingenlargement entering into said conduit.

'7. The combination with a spark plug, of a radio shielding casingtherefor, a metal radio shielding conduit for a conductor cable to saidspark plug, a conductor cable extending through said conduit and intosaid casing, an integral, tubular, resilient, flexible, duid-impervious,insulating bushing through which said cable passes, said bushing havingan outwardly extending enlargement intermediate its ends and cylindricalportions of less diameter on each side of said enlargement, saidenlargement resiliently pressing against said casing and said conduit,one of said cylindrical portions of the said bushing extending into saidconduit upon one side of said enlargement and the other of saidcylindrical bushing portions extending into said casing upon the otherside of said enlargement, means for securing said conduit and casingtogether with said bushing enlargement resiliently bearing upon saidconduit and casing and means at the end of said cable for connecting itwith an electrode of the spark plug, said bushing enlargement enteringinto said casing.

8. The combination with a plurality of radio f shielding conduits, of aconductor cable therein, an integral, tubular, resilient, flexible,fluid-impervious, insulating bushing about said cable, said bushinghaving an outwardly extending enlargement intermediate its ends andcylindrical portions of less diameter on each side of said enlargement,said enlargement resiliently pressing against both of said conduits, oneof said cylindrical bushing portions extending into one of said conduitsand the other` of saidcylindrical bushing portions extending into theother of said conduits and means for holding said conduits together withsaid bushing enlargement resiliently bearing upon both of said conduits.

9. The combination with a plurality of radio shielding conduits, of aconductor cable therein, an integral, tubular, resilient, exible,fluid-impervious, insulating bushing about said cable, said bushinghaving an outwardly extending enlargement intermediate its ends andcylindrical portions of less diameteron each side of said enlargement,said enlargement resiliently pressing against both of said conduits, oneof said cylindrical bushing portions extending into one ot said conduitsand the other of said cylindrical bushing portions extending into theother o! said conduits and means for holding said conduits together withsaid bushing enlargement resiliently bearing upon both of said conduits,one of said conduits being curved.

10. The combination with a plurality of radio shielding conduits, of aconductor cable therein, an integral, tubular, resilient, ilexible,fluid-impervious, insulating bushing about said cable, said bushinghaving an outwardly extending enlargement intermediate its ends andcylindrical portions of less diameter on each side of said enlargement,said enlargement resiliently pressing against both of said conduits, oneof said cylindrical bushing portions extending into one oi' saidconduits and the other o! said cylindrical bushing portions extendinginto the other o! said conduits and means for holding said conduitstogether with' said bushing enlargement resiliently bearing upon bothoi' said conduits, the said bushing enlargement entering partially intoone of said conduits.

11. The combination with a plurality of radio shielding conduits, of aconductor cable therein, an integral, tubular, resilient, flexible,uid-impervious, insulating bushing about said cable,

said bushing having an outwardly extending enlargement intermediate itsends and cylindrical portions of less diameter on each side of saidenlargement, said enlargement resiliently pressing against both of saidconduits, one of said cylindrical bushing portions extending into one ofsaid conduits and the other of said cylindrical bushing portionsextending into the other of said conduits and means for holding saidconduits together with said bushing enlargement resiliently bearing uponboth of said conduits, the said bushing enlargement entering partiallyinto each of said conduits.

l2. The combination with a plurality of radio shielding conduits, oi' aconductor cable therein, an integral, tubular, resilient, exible,fluidimpervious, insulating bushing about said cable, said bushinghaving an outwardly extending enlargement intermediate its ends andcylindrical portions of less diameter on each side of said enlargement,said enlargement resiliently pressing against both of, said conduits,one of said cylindrical bushing portions extending into one of saidconduits and the other of said cylindrical bushing portions extendinginto the other of said conduits and means for holding said conduitstogether with said bushing enlargement resiliently bearing upon both ofsaid conduits, said tubular bushing resiliently pressing on said cable.

13.*The combination with a curved, tubular, metal radio shieldingconduit, of a conductor cable extending therethrough and an intergal,tubular, resilient, flexible. duid-impervious, insulating bushing aboutsaid cable, said bushing comprising an outwardly extending enlargementintermediate its ends and cylindrical portions of less diameter on eachside o! said enlargement, one of said cylindrical portions and at leasta portion of said enlargement extending within said conduit and theother of said cylindrical bushing portions extending outside saidconduit, and means adjacent the end of the last mentioned cylindricalbushing portion connected with the conductor of said cable and adaptedto establish connection thereof with a spark plug.

14. A bushing for a radio shielding conduit connection, said bushingbeing integral, tubular, resilient, flexible, fluid-impervious andinsulating, the said bushing having an interior bore adapted toresiliently bear upon a conductor cable passing through the connectedconduits and said bushing comprising an outwardly extending enlargementintermediate its ends adapted to bear resiliently against both theconnected conduits to seal them from the exterior and from each otherand cylindrical portions of less diameter, one on each side of saidenlargement, one of said cylindrical portions being adapted to extendinto one of the connected conduits and the other of said cylindricalportions being adapted to extend into the other of the connectedconduits.

l5. A bushing for a radio shielding conduit connection, said bushingbeing integral, tubular, resilent, flexible, Huid-impervious andinsulating, the said bushing having an interior bore adapted toresiliently bear upon a conductor cable passing through the connectedconduits and said bushing comprising an outwardly extending enlargementintermediate its ends adapted to bear resiliently against both theconnected conduits to seal them from the exterior and from each otherand cylindrical portions of less diameter, one on each side of saidenlargement, one of said cylindrical portions being adapted to extendinto one of the connected conduits and the other of said cylindricalportions being adapted to extend into the other of the connectedconduits, one of said cylindrical portions being of less outsidediameter than the other of said cylindrical por tions.

DAVID INGALLS.

